Devices to invert objects are known and are used in many industries. For example, Pritchard U.S. Pat. No. 4,220,239 teaches a device for inverting sheets of gypsum board during their manufacturing process. A set of lifting arms engage the lower surface of a sheet of green gypsum board and rotate it about one edge to a vertical position wherein a set of catcher arms engage the other surface of the gypsum board. The catcher arms then continue rotation of the gypsum board to place it onto an adjacent conveyor belt with the surface which was previously underneath now being on top.
Trigg et al. U.S. Pat. No. 3,552,538 shows another device for inverting flat articles such as sheets of drywall, etc. The device comprises a pair of lifting arms and a pair of rear arms which are arranged along a conveyor. The leading edge of a flat article travelling along the conveyor is lifted by the lifting arms with the trailing edge of the article resting on the rear arms. The leading edge of the article is rotated through a vertical position until the article abuts a rearwardly inclined surface, at which point the trailing edge of the article engages the lifting arms which lower the trailing edge to engage the conveyor, thereby returning the article to a horizontal, inverted position on the conveyor.
However, problems exist with the prior art devices for inverting planar objects of which the present inventor is aware. Specifically, the prior art devices are only operable to invert the position of an article and cannot re-invert the article if such should be desirable or required. Further, the prior art devices invert the article by moving the article from one side of the device to the other side and thus require a clear area about the device of at least twice the size of the article.
It is therefore desirable to have an apparatus which is operable to position a substantially planar object in a horizontal position wherein either side is facing up, as desired, and to reposition the article so that the other side faces up.